A new patent from Google published today has some fascinating insight into how the company thinks that production of self-driving cars of the future might take control from the drivers they’re shuttling around — and how they could give it back, too.

The description of “Google Chauffeur,” spotted by Stanford’s Reilly Brennan, is a pretty straightforward concept. An arm on the steering column (not much different from a windshield wiper arm) could be pulled to engage a car’s self-driving mode; at that point, the system would do a check to see whether it’s ready and able to actually take control from the driver. If it isn’t — the car can’t get a GPS lock, for instance — the driver might see a “Not Available” light on the dash. Otherwise, you’d see a “Ready” light, at which point you can start taking your appendages off the wheel and pedals. (The focus of the patent’s coverage is on the operation of these lights, but the remainder of the patent’s text gives interesting insight into how Google sees a car actually working.)